The present invention relates to a gear box for use in conjunction with a water pump and, more particularly, to such a gear box that is operative in response to rotation of an input shaft such as, for instance, by a crank-type handle.
Various types of hand pumps are known for pumping water from an underground supply in addition to the traditional, reciprocating "farmyard" pump. Among these is the progressing cavity pump, wherein a screw-like helical rotor turns eccentrically within a helical stator. The stator is constructed of a resilient material, so that as the rotor is turned, a plurality of sealed cavities progress upwardly through the stator, carrying water within each cavity. This type of pump is generally more rugged and reliable than the reciprocating pump, since it has fewer moving parts, and thus is often preferred in remote pump installations.
Power is applied to such a pump from above ground by rotating a vertical drive shaft extending into the well and connected to the pump rotor. In installations where hand operation is desired, the shaft may be rotated by a pair of rotating handles attached to a horizontal input shaft. Power is transferred through a right angle gear box to the vertical shaft.
Care must be taken, however, to prevent the handles from being rotated in the wrong direction. In such a case, threaded connections in the horizontal or vertical shafts can become disconnected, rendering the pump inoperative. Additionally, in deep wells it is possible for the head of water in the pump to cause the pump rotor to motor when the handles are released. Thus, the handles could rotate when released. Consequently, hand pump designs of this type usually include a backstop device to permit the horizontal shaft carrying the handles to be rotated in only one direction.
Various backstop devices have been used. A simple lever may be provided for engaging a step in a cam affixed to the handle shaft whenever the handles are rotated in the wrong direction. More sophisticated devices, such as roller or ball bearing clutches, have also been used. In each case, however, the maximum torque or load the backstop could be subjected to is limited. Thus, it is possible to damage the backstop to the extent that the backstop fails to operate, which can ultimately result in failure to the pump.
In remote, underdeveloped areas, where the consequences of pump failure may be most severe, the pump user is often not technically sophisticated enough to appreciate the risk associated with incorrect rotation of the handles. Moreover, the backstop device may not be readily understood by the user, resulting in undue force being exerted thereupon, often leading to failure of the device.
What is needed, therefore, is a gear box for use in conjunction with a water pump that will prevent pump failure caused by operation of pump elements in the reverse direction by allowing the pump handles to be rotated in either direction. Such a gear box would eliminate the need for backstop devices to prevent rotation of the pump handles in the wrong direction.